> I have some high power fast switching transistors, BUV48, which I want to
> use to control a 220V DC motor using PWM. The transistor can handle 10A Ic
> and 400 Vce (hfe =8!!). My problem is that the motor draws up to 20A and
> thus I will
> need more than one of these transistors in possibly a darlington
> configuration. Please can someone help me with a circuit to control this
> current hungry motor using a pic ...

This is the kind of thing that if you need to ask about you shouldn't be
messing with.  You can't just parallel bipolar transistors because they
won't share the current equally.  The current imbalance is actually
amplified by the thermal characteristics.  This is usually dealt with by
giving each transistor its own emitter resistor.  100mOhms might be OK in
your case.  That can be implemented by a measured length of the right wire.
I don't like darlington for this because of the larger voltage accross the
transistors when on.  At 10A that makes quite a few watts of difference.  If
you are really stuck on these transistors, I would use at least 3 of them
and give them good heat sinks.  The base drive circuit alone will need to
switch over 3A.

Again, there are lots of issues here.  Get someone to do this that knows
what they are doing.


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